1. Field of the Invention
The present invention relates to a liquid crystal display device, and in particular, relates to a liquid crystal display device including linear (comb-like) electrodes with differing inclination angles within the same pixel.
2. Description of the Related Art
A liquid crystal display device called an in-plane switching (IPS) type or lateral electric field type is configured so that a pixel electrode and common electrode disposed opposed to each other across an insulating film are formed on the same planar substrate. The IPS type liquid crystal display device is configured so that an electric field having components parallel to the principal surface of the planar substrate is generated between the pixel electrode and common electrode, and liquid crystal molecules are driven by the electric field, and is known for enabling a wide viewing angle display. With the IPS type liquid crystal display device, a transparent electrode in which a plurality of slits are formed is formed across an insulating film on the liquid crystal side of a planar common electrode formed by a transparent conductive film, and this configuration allows a formation of a linear (comb-like) pixel electrode superimposed over the planar common electrode.
In recent years, a further improvement in display quality has been demanded, and an improvement in aperture ratio has been demanded in order to improve a dynamic range range. As a liquid crystal display device with an improved aperture ratio, for example, a configuration is such that one drain line is formed for every two pixel columns disposed adjacent to each other, and video signals are supplied, time-shared, to pixels disposed on either side of the drain line. Furthermore, there is a liquid crystal display device in which pixels are formed so as to be displaced by half a pitch in an extension direction of a gate line (an extension direction of a drain line) every other row (column), thereby reducing defective displays accompanying an occurrence of so-called vertical streaks caused when video signals are supplied time-shared. As a liquid crystal display device in which pixels are disposed displaced by half a pitch in the extension direction of the gate line every other row (column), there is, for example, a liquid crystal display device described in JP 6-289423 A.
Meanwhile, as a technology of improving the viewing angle of the IPS type liquid crystal display device, there is a so-called multi-domain type wherein the inclination angles of slits SLT opened along a gate line GL are formed with inclination angles differing in a region close to and a region far from a thin film transistor TFT within a rectangular pixel region, as shown in FIG. 8. However, when the slits SLT opened in the direction of the gate line GL are formed, it is necessary to form a pixel electrode having the slits SLT to be large in the extension direction of the slits in order to improve the aperture ratio. However, when the gap between pixel electrodes of adjacent pixels becomes smaller, the effect of a diving voltage between adjacent pixels becomes higher, and there is fear that a difference in effective voltage occurs between the adjacent pixels, causing vertical streaks.
As a method of solving this problem, there is a multi-domain method whereby slits are formed in a direction perpendicular to a gate line (a direction of pixel columns) with inclination angles differing in a region close to and a region far from a thin film transistor within a pixel region, and the slits with the differing inclination angles are linked, forming a linear electrode PX in a dogleg form, as shown in FIG. 9.
However, with this type of pixel electrode PX, it is known that it is possible to increase a gap L between pixel electrodes, but that, an electric field being disturbed in a boundary region, shown by the dotted-line circle, in which the inclination angle of the slits changes, it is not possible to carry out a normal image display, and in particular, an occurrence of a so-called push domain is known wherein back light is transmitted by pressing a liquid crystal display device from the normal direction thereof. As an improvement method thereof, as shown in FIG. 10, a method is known whereby slits SLT with inclination angles differing in a region close to and a region far from a thin film transistor within a pixel region are formed, and an electrode TT is formed in a boundary region, but the region in which the electrode TT is formed is a region which does not contribute to an image display, meaning that there is fear that the aperture ratio decreases.